Full coverage of a second generation (2G) or a third generation (3G) network such as a Global System for Mobile Communications (GSM) or Wideband Code Division Multiple Access (WCDMA) is basically implemented.
With development of Long Term Evolution (LTE) network technologies, these LTE networks already cover some urban areas and traffic hotspot areas. In this way, in current communications networks, an LTE network and a 2G or 3G network coexist.
During a call, user equipment (UE) may enter a 2G or 3G network from an LTE network. Because the LTE network and the 2G or 3G network have different bearer mechanisms, the user equipment needs to be handed over from a packet switched (PS) domain to a circuit switched (CS) domain. Therefore, a voice call may be interrupted, affecting continuity of the voice call of a user.
A circuit switched fallback (CSFB) refers to that when user equipment (UE) in coverage of LTE processes a voice service, the UE first falls back to a network having a CS domain and processes the voice service in the network having a CS domain. In this way, an objective of reusing an existing CS domain device to provide a conventional voice service to a user in an LTE network is achieved. In the prior art, the UE needs to be handed over from the LTE network to a PS domain of the 2G or 3G network or be redirected from the LTE network to the 2G or 3G network, and then initiate, in the 2G or 3G network, a connection to a CS domain.
In the prior art, a CSFB process includes a CSFB for a voice service and a CSFB for a non-voice service. However, in the prior art, voice resource waste is caused during implementation of a CSFB service for a non-voice service.